Heat the oven to 350°F (175°C) with a rack in the center. Line a 9-inch/22 cm square baking pan with parchment, leaving an overhang on two sides.
In a stand mixer fitted with the paddle attachment, or in a large bowl using your fingertips, combine the flour, powdered sugar, butter, and salt. Mix just until the dough comes together and no dry spots remain. Press the dough evenly into the prepared pan. Prick it lightly all over with a fork and bake for 15 minutes, until pale golden.
In a medium saucepan over medium heat, combine the brown sugar, maple syrup, honey, cream, butter, and salt. Cook, stirring often, until the mixture is smooth and begins to bubble, about 3 to 4 minutes. Remove from the heat and stir in the chopped pecans.
Pour the topping over the hot crust and spread evenly. Return the pan to the oven and bake for 18 to 22 minutes, until the edges are bubbling and the top is glossy and darkened slightly.
Cool completely in the pan on a rack. Use the parchment to lift the slab onto a cutting board, then slice into 16 bars with a sharp knife.